1. Field of the Invention
The present invention relates to a semiconductor memory device, and more particularly, to a semiconductor memory device having row and column decoders for decoding row and column address signals without generating leakage current in stand-by mode.
2. Description of the Related Art
A semiconductor memory device includes a memory cell array, a row decoder, a column decoder, sense amplifiers and data input/output lines. A memory cell array includes a plurality of memory cells connecting with word lines and pairs of bit lines for accessing data in the memory cells. The pairs of bit lines are electrically connected to the sense amplifiers under control of column selection lines from a column decoder. A row decoder decodes a row address signal received from an external source to select some of the word lines. A column decoder decodes a column address signal received from an external source to select some of the column selection lines. The row decoder is connected to drivers to drive the word lines, and the column decoder is connected to drivers to drive the column selection lines.
In a semiconductor memory device utilizing a low supply voltage, the widths of the gates of MOS (metal oxide semiconductor) transistors in row and column decoders are very small. Thus, when a slight voltage difference exists between a source and a drain of a MOS transistor while the row and column decoders are in a stand-by state, a small leakage current is generated from the MOS transistor. Since the amount of such leakage current is small, the leakage current little affects power consumption of a semiconductor memory device when the number of row and column decoders in the semiconductor memory device is small. However, the amount of leakage current increases with an increase in the number of row and column decoders in a semiconductor memory device, so that power consumption of the semiconductor memory device also increases. As larger semiconductor devices are used in applications with finite power sources, such as portable or laptop computers, the larger leakage current becomes a factor affecting performance and/or appeal.
Therefore, it would be advantageous to provide a semiconductor device having decoders for decoding row and column address signals which do not generate leakage current in a stand-by state, thereby reducing power consumption of the semiconductor device. It is also desirable to provide a semiconductor device with improved row and column decoders which do not affect the size of the semiconductor device, even in a high-integrated semiconductor device.